Functional molecular element

ABSTRACT

A functional molecular element is provided. The functional molecular element is adapted to change, by application of electric field, conformation of a disc shape like organic metallic complex molecule ( 1 ) which forms a columnar arrangement structure to exhibit function, wherein the structure of the organic metallic complex molecule is changed by application of electric field so that anisotropy of dielectric constant is changed. Accordingly, conductivity between measurement electrodes can be switched. As its stable value, there are three kinds of stable values or more. Thus, elements or devices to which such multi-value memory characteristic is applied can be constituted.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent Document No.P2004-033055 filed on Feb. 10, 2004, the disclosure of which is hereinincorporated by reference.

The present invention relates to a novel functional molecular elementwhich exhibits function under action (application) of electric field.

This Application claims priority of Japanese Patent Application No.2004-033055, field on Feb. 10, 2004, the entirety of which isincorporated by reference herein.

In general, nano-technology is recognized as technology for observing,preparing (manufacturing) and utilizing fine structure having size ofthe order of one hundred millionth (10⁻⁸ m=10 nm).

In the latter half of the year of 1980, ultra-high precision microscopescalled scanning type tunnel microscopes have been invented so that oneatom and/or one molecule can be observed. If such scanning type tunnelmicroscopes are used, not only atoms or molecules can be observed, butalso atoms or molecules can be operated (manipulated) one by one.

For example, the example where atoms are arranged on the surface ofcrystal to write characters, and the like have been reported. However,even if it can be said that atoms or molecules can be operated ormanipulated, it is not practical to operate or manipulate, one by one, ahuge number of atoms or molecules to assemble new materials (substances)or devices.

In order to operate or manipulate atoms or molecules, or cluster thereofto form a structure of the nanometer size, a new ultra precisionprocessing technology to realize such a structure is required. As such afine processing technology of the nanometer precision, two systems areknown when roughly classified.

One system is a method conventionally used in manufacturing processesfor various semiconductor devices. This method is, e.g., such a methodof the so-called top-down type to precisely shave a large silicon waferdown to the minimum size to prepare integrated circuits. The othersystem is a method of the bottom-up type to assemble atoms or moleculesas small parts or components serving as micro (very small) unit tomanufacture a target nano-structure.

In connection with the limit as to what structure of small size can bemanufactured by the top-down system, there is the famous Moore's Lawthat Gordon Moore who is co-creator of Intel Corporation has presentedin 1965. This rule is the content that “the degree of integration oftransistor becomes double in eighteen months”. Since 1965 (year), thesemiconductor business world has enhanced degree of integration oftransistor in accordance with the Moore's Law over thirty years.

International Technology Roadmap for Semiconductor (ITRS) for fifteenyears in future announced from the U.S. Semiconductor IndustrialAssociates (SIA) indicates the opinion that the Moore's Law iscontinuously valid.

The ITRS consists of short-range roadmap until 2005 (year) andlong-range roadmap until 2014 (year). In accordance with the short-rangeroadmap, process rule of the semiconductor chip is assumed to becomeequal to the order of 100 nm and the gate length of the microprocessoris assumed to become equal to 65 nm in 2005. In accordance with thelong-range roadmap, the gate length is assumed to becomes equal to 20˜22nm in 2014.

As miniaturization of the semiconductor chip is advanced, operatingspeed becomes high and power consumption is suppressed at the same time.Further, the number of products (chips) taken from a single wafer isincreased and the production cost is also lowered. This is becausemakers for microprocessors compete the process rule and the degree oftransistor integration of new products.

On November in 1999, the research group of USA indicated epoch-makingresearch result of miniaturization technology. The research result isdirected to a method of designing gate of FET (Field Effect Transistor)called FinFET, which has been developed by the group including ProfessorChainmin Fuh, et al. who is in charge of Computer Science at BarkleySchool of California University. This method enables formation oftransistors which are 400 times greater than that in the prior art on asemiconductor chip.

The gate is an electrode for controlling flow of electrons at thechannel of FET, and is caused to be of structure, according to presenttypical design, in which the gate is placed in parallel to the surfaceof the semiconductor and serves to control the channel from one side. Inthis structure, it was considered that since if the gate has not apredetermined length or more, it is impossible to cut off (interrupt)flow of electrons, gate length therefore constitutes one cause (factor)to limit miniaturization of transistor.

On the contrary, in the case of the FinFET, the gate is caused to be offork type bridging over both sides of the channel to effectively controlthe channel. In the structure of the FinFET, the gate length and thetransistor can be further reduced as compared to the conventionalstructure.

The gate length of the FET of the prototype that the same research groupas above has manufactured is 18 nm, which is one tenth of presenttypical gate length. This gate length is equivalent to the size in 2014(year), which is indicated by the long-range roadmap of ITRS. Further,it is said that gate length which is one half thereof may be realized.Since Fuh, et al. do not have intention to acquire the patent inanticipation that such structure will be widely employed in thesemiconductor business world, there is also the possibility that theFinFET may also become main current of the manufacturing technology.

However, it is also pointed out that “Moore's Law” might reach the limitbased on the natural law after all.

For example, in the semiconductor technology which is main current atpresent, circuit patterns are baked on silicon wafer by the lithographytechnology to manufacture semiconductor chip. In order to realizefurther miniaturization (fine structure), resolution must be increased.In order to increase resolution, a technology utilizing light havingshorter wavelength must be put into practice.

Moreover, calorific value per semiconductor chip may become too largewith increase of the degree of integration. As a result, thesemiconductor chip caused to have high temperature may be erroneouslyoperated, or thermally broken.

Further, in accordance with prediction by the specialist, it is alsoconsidered that when the semiconductor business world continues tominiaturize (reduce) chip as it is, the facility cost and/or the processcost are increased so that manufacturing of semiconductor chip mightbecome impossible from an economical point of view in about 2015 alsosince deterioration of yield is invited in addition to the above.

As a new technology for overcoming technical obstacle of the top-downsystem as described above, the spotlight of attention is focused onresearch for allowing individual molecules to have functions aselectronic parts (components). Devices based on such research or studyare electronic device consisting of single molecule (molecular switch,etc.), and are manufactured (fabricated) by the bottom-up system.

Also with respect to metal, ceramics and/or semiconductor, researches(studies) for preparing (manufacturing) structure of nano-meter size bythe bottom-top system are being performed. However, if attention isdrawn to molecules which are primarily and individually independent andhave variety to the number of about several million kinds in differenceof shape and/or difference of function, etc. to exhibit the propertiesthereof, it is possible to design, by the bottom-up system, devices(molecular devices) having features entirely different from conventionaldevices to manufacture such devices.

For example, width of conductive molecule is only 0.5 nm. Wire of thismolecule enables realization of wiring having density which is severalthousands times than that of line width of about 100 nm which isrealized by the present integrated circuit technology. Moreover, when,e.g. one molecule is used as memory element (device), recording which isten thousands times or more than that of DVD (Digital Versatile Disc)can be made.

Molecular devices are synthesized by chemical process differently fromthe conventional semiconductor silicon. In 1986, Yuji Hizuka ofMitsubishi Denki Kabushiki Kaisha has developed the first organictransistor consisting of polythiophene (polymer) in the world.

Further, search group of U.S. Hewlett-Packard (HP) Corporation and LosAngeles school of California University succeeded manufacturing oforganic electronic device and announced the content thereof in ScienceMagazine on July in 1999. Such organic devices are disclosed in U.S.Pat. No. 6,256,767 specification and U.S. Pat. No. 6,128,214specification. They made (fabricated) switches by using molecular filmsconsisting of several millions of rotaxane as organic molecule toconnect these molecular switches to make AND gate serving as a basiclogical circuit.

In addition, cooperative search group of the Rice University and theYale University in U.S.A. succeeded to make molecular switch in whichmolecular structure is changed by electron injection under applicationof electric field to perform switching operation and announced suchmolecular switch in the Science Magazine on November in 1999 (J. Chen,M. A. Reed, A. M. Rawlett and J. M. Tour, “Large on-off ratios andnegative differential resistance in a molecular electronic device”,Science, 1999, Vol. 286, 1551-1552, J. Chen, M. A. Reed, C. Zhou, C. J.Muller, T. P. Burgin and J. M. Tour, “Conductance of a molecularjunction”, Science, 1997, Vol. 278, 252-2). The function to repeatedlyperform on-off operation is a function which was not realized by thegroup of HP (Hewlett-Packard) Corporation and Los Angeles school ofCalifornia University. The size thereof is one millionth of ordinarytransistor, and constitutes basis for manufacturing small and highperformance computer.

Professor J. Tour (Rice University, Chemistry) who succeeded synthesisstated that since high cost clean room used for ordinary semiconductormanufacturing process is unnecessary, production cost of molecularswitch can be reduced down to one several thousandth of prior art.Within five to ten years, he has a schedule to make hybrid type computerof molecule and silicon.

In 1999, Bell Laboratory (Lucent Technology Corporation) fabricatedorganic thin film transistor by using pentacene single crystal. Thisorganic thin film transistor exhibited the characteristic equivalent toinorganic semiconductor.

Although it is said that studies or researches of molecular devicehaving a function as electronic component are extensively beingperformed, most of studies relating to molecular devices until now weredirected to studies in which drive is performed by light, heat, protonor ion, etc. (Ben L. Feringa, “Molecular Switches”, WILEY-VCH, Weinheim,2001).

As conventional molecular element driven by electric field, there onlyexisted element utilizing change of material property of molecule itselfwhich has been caused to undergo action (application) of electric field,i.e., element in which electronic state of molecule itself considered tobe single element is changed by electric field. For example, in organicFET, carrier transfer (movement) in organic molecule is modulated bychange of electric field exerted on organic molecule within the channelarea.

In view of actual circumstances as described above, an object of thepresent invention is to provide a functional molecular element (device)effectively controlled by electric field on the basis of a newprinciple.

SUMMARY

The present invention is directed to a functional molecular element inwhich anisotropy of dielectric constant is changed by molecularstructure change induced by electric field.

In the present invention, since functional molecular element isconstituted by using the system in which anisotropy of dielectricconstant is changed by molecular structure change induced by electricfield, the electric characteristic as a functional molecular element,e.g., conductivity, etc. can be obtained, and its electriccharacteristic is modulated by change of molecular structure induced bychange of the electric field.

Such mechanism of action of electric field is directed to a mechanismadapted to directly control, by electric field, dielectric constant ofthe functional molecular element to modulate its function, and is notfound out in conventional functional molecular element or device, e.g.,Field Effect Transistor, etc. On the basis of new electric field actionmechanism, it is possible to constitute functional molecular elementwhich can control electric characteristic with high response of electricfield.

Still further objects of the present invention and merits obtained bythe present invention will become more apparent from embodiments whichwill be explained below with reference to the attached drawings

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription and the Figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A to 1C are schematic diagrams illustrating three switchingoperation modes that functional molecular element according to thepresent invention indicates, wherein FIG. 1A shows the initial statewhere no electric field is applied, FIG. 1B shows the state where lowelectric field (voltage) is applied, and FIG. 1C shows the state wherehigh electric filed (voltage) is applied.

FIG. 2 is a view showing structural formula of biladienone metalliccomplex constituting functional molecular element.

FIG. 3 is a model view showing model of chemical structure ofbiladienone metallic complex and spiral structure thereof.

FIG. 4A shows a schematic cross sectional view of Field Effect typemolecular device to which the present invention is applied, and FIG. 4Bis a plane view of comb-shaped electrode.

FIG. 5 is a schematic cross sectional view showing, in an enlargedmanner, the essential part of the Field Effect type molecular device.

FIG. 6A is a schematic perspective view showing the behavior at the timewhen voltage of the Field Effect type molecular device is turned ON, andFIG. 6B is a schematic perspective view showing the behavior whenvoltage of the Field Effect type molecular device is turned OFF.

FIG. 7 is a graph showing, every ON/OFF time, the relationship betweencurrent and voltage of Field Effect type molecular device according tothe practical example 1 of the present invention.

FIG. 8 is a graph showing the relationship between dielectric constantand voltage of the Field Effect type molecular device.

FIG. 9 is a graph showing the relationship between current and voltageof Field Effect type molecular device according to the comparativeexample 1 of the present invention.

DETAILED DESCRIPTION

As functional molecular element according to the present invention, itis preferable to use organic metallic complex molecule of desirablydisc-shaped, or disc-shape like organic molecule having, e.g., sidechains in normal (straight) chain form having anisotropy of dielectricconstant and adapted so that structure is changed under action(application) of electric field, and metallic ion. The fact that theorganic molecule has dipole moment also results in action equivalent toanisotropy of dielectric constant.

If organic molecule in a form similar to disc shape having such sidechains is used, the property of discotic liquid crystal is indicated sothat orientation of molecules takes place. Thus, anisotropy of highdielectric constant can be exhibited. With respect to this, there can bereferred, ‘S. T. Trzaska, H-F. Hsu and T. M. Swager, “CooperativeChiralith in Columnar Liquid Crystals Studies of Fluxional OctahedralMetallomesogens.”, J. Am. Chem. Soc., 1999, Vol. 121, 4518-4519, and YoShimizu “Columnar Liquid Crystals: Versatile molecular structuresthereof and Intermolecular interaction”, Liquid Crystals, 2002, Vol. 6,147-159 which will be described later’.

On the other hand, since the organic molecule has anisotropy ofdielectric constant and the structure or orientation thereof is changedunder application of electric field so that conformation of portionwhere complex is formed, etc. is changed in correspondence with changeof the electric field. Thus, anisotropy of dielectric constant, i.e.,electric characteristic is changed.

Further, it is preferable that liquid crystal solution of disc-shapelike organic metallic complex molecules having side chains is disposedbetween at least opposite electrodes in the state where orientationthereof is performed on the electrode for applying electric field sothat an output corresponding to the electric field is taken out from atleast one electrode of the opposite electrodes.

Further, it is preferable that there is formed columnar arrangementstructure in which disc-shape like organic metallic complex moleculeshaving side chains are arranged in columnar form between these pair ofopposite electrodes.

Moreover, it is preferable that the structure of the organic metalliccomplex molecule is changed by change of an electric field exerted ondisc-shape like organic metallic complex molecule having side chains sothat an angle that the major axis direction of the dielectric constanttensor and the formation plane surface of the pair of oppositeelectrodes form is changed.

In this case, it is preferable that an insulating layer is provided on afirst electrode for applying electric field, second and third electrodesare formed, as the opposite electrodes, on the insulating layer in sucha manner that they are not in contact with each other, a columnararrangement structure is disposed between at least these second andthird electrodes, and a fourth electrode for applying the electric fieldis provided directly or through insulating layer on disc shape likeorganic metallic complex molecule having side chains which forms thecolumnar arrangement structure.

Moreover, it is preferable that disc-shape like organic molecule havingside chains is biladienone derivative such as biliverdin or biladienone,etc., and metallic ion is zinc ion, copper ion or nickel ion, etc.

In addition to the biladienone derivative, there may be used bilinderivative, florine derivative or chlorine derivative, etc. As theabove-mentioned metal, there may be used other typical element and/ortransition metal.

Further, the side chain may have normal (straight) shape having thenumber of carbon atoms of 3 to 12. For example, —C₁₀H₂₁ or —C₈H₁₇ may bementioned. By side chain having such number of carbon atoms, orientationof organic molecules can be satisfactorily performed withoutcrystallization. Synthesis also becomes easy. Namely, when the number ofcarbon atoms is 1˜2, organic molecule becomes easy to be crystallized sothat material property like liquid crystal is not exhibited. As aresult, unsatisfactory orientation takes place. Moreover, when thenumber of carbon atoms becomes equal to 13 or more, organic molecule isdifficult to rather undergo orientation. Synthesis also becomesdifficult.

Further, as solvent used in solution, there may be used, e.g., polarsolvent, e.g., biphenyl-system liquid crystal such as4-pentyl-4′-cyanobiphenyl (5CB) or tetrahydrofuran, etc. It ispreferable that concentration of organic molecule such as biladienonemetallic complex, etc. in this liquid crystal solution is 0.1˜80 weight%. Further, it is desirable that such concentration is 10˜30 weight %.

It is to be noted that the above-described “functional molecularelement” is not limited to element constituted as element, but may alsoinclude molecular device as previously described in which such elementis assembled (This similarly applies to hereinafter).

Then, preferred embodiments of the present invention will be explainedin concrete terms with reference to the attached drawings.

Embodiment 1 Functional Molecular Element

As an example of function of molecular element in whichthree-dimensional structure is changed by application of an electricfield to exhibit function, switching operation is conceivable. FIGS. 1Ato 1C schematically illustrate, in a model form, change taking place atthe periphery of metallic ion 3 at the time of applying an electricfield to the functional molecular element 1 by taking an example of thefunctional molecular element 1 in which metallic ion 3 and disc-shapelike organic molecule 2 having side chains 5 form complex 4.

Since disc-shape like organic metallic complex molecule having sidechains 5 (functional molecule 1) has plural activity portions withrespect to metal 3, there exist plural structural isomers havingproduction energies substantially equal to each other. In the initialstate where no electric field (voltage) is applied as shown in FIG. 1A,the organic metallic complex molecule takes structure 1 a having lowestproduction energy.

However, when, e.g., low electric field (voltage) is applied, theorganic metallic complex molecule 1 performs structural change balancedwith its production energy difference and applied electric field(voltage) strength in such a manner that there results structure 1 b inwhich anisotropy of dielectric constant is along applied electric fielddirection (electric field application direction) in attempting to allowdielectric constant anisotropy to be in correspondence with appliedelectric field direction as shown in FIG. 1B.

Further, when, e.g., higher electric field (voltage) is applied, theorganic metallic complex molecule performs structural change in such amanner that there results structure 1 c in which its production energyis high and dielectric constant anisotropy is caused to be, to moredegree, in correspondence with electric field application direction asshown in FIG. 1C.

As stated above, with respect to dynamics of the switching operationthat the functional molecule exhibits at the time of application ofelectric field, at least two kinds of operation modes shown in FIGS. 1B,1C are conceivable depending upon difference of electric field strength.This will be further explained in detail.

In the initial state where no voltage is applied as shown in FIG. 1A,disc-shape like organic metallic complex molecule 1 a having side chains5 of the functional molecular element 1 attempts to take circularstructure which is closed as close as possible.

When electric field (voltage) is applied as shown in FIG. 1B in thisstate, the disc-shape like organic metallic complex molecule 1 havingside chains 5 attempts to take, e.g., opened (expanded) circularstructure 1 b in such a manner that direction of dielectric constantanisotropy attempts to become in correspondence with direction ofelectric field. Moreover, when higher electric field (voltage) isapplied as shown in FIG. 1C, the structure of the organic metalliccomplex molecule 1 changes into extended circular structure 1 c in amanner to allow direction of dielectric constant anisotropy to befurther in correspondence with electric field application directionwhile production energy is higher than that at the time when no electricfield is applied.

When such state is viewed as the entirety of column, there is performeda change as if spiral pitch expands or contracts.

As described above, the structure or orientation of disc-shape likeorganic metallic complex molecule 1 having side chains is changed byapplication of electric field. This causes change in the structure ofthe complex formation part 4 with respect to metallic ion 3 to changedielectric constant, i.e., conductivity of the functional molecule 1.

As the functional molecule 1, several combinations are conceivabledepending upon difference of the configuration, etc. of disc-shape likeorganic molecule 2 having side chains 5 or complex formation part 4,etc.

For example, FIG. 2 shows organic metallic complex molecule 1 ofdisc-shape like organic molecule 2 having side chains 5 consisting ofsubstituent (R) (e.g., —C₁₀H₂₁), e.g., biladienone derivative having C═Ogroup facing to each other at the terminal end thereof and metallic ion(M), e.g., Zn (II) ion.

In this organic metallic complex molecule 1, molecules take twistedstructure by existence of C═O group (carbonyl group) of end terminalsfacing to each other, and plural molecules takes π-π stack structuretherebetween to wind spiral. In FIG. 3, model of the molecular structurethereof is shown. In this case, the spiral structure is formed byoptical isomer of M-group or P-group. Pitch between molecules of thespiral structure is changed by action (application) of the electricfield.

This organic metallic complex 1, e.g., biladienone metallic complextakes blue in the ordinary state where no electric field (voltage) isapplied, and causes change of green→thin brown by application ofelectric field. In addition, when electric field is cut OFF, the organicmetallic complex 1 reversibly returns to the original state. It is to benoted that such change takes place also by temperature, and it istherefore considered that when both electric field and temperature arecontrolled, molecular structure may be similarly changed.

Embodiment 2 Field Effect Type Molecular Device

Here, as disc shape like organic metallic complex molecule 1 which formscolumnar arrangement structure, there is used complex of biladienone 2and zinc (II) ion as metallic ion 3, which is used in FIG. 2, and aField Effect type molecular device 21 in which such complex is assembledas shown in FIGS. 4A and 4B and a manufacturing process thereof will beexplained.

FIG. 4A is a schematic cross sectional view showing the structure of theField Effect type molecular device 21, and FIG. 4B shows comb-shapedelectrodes 33 and 34 used therein. FIG. 4A is a schematic crosssectional view in which the Field Effect type molecular device 21 is cutalong A-A line shown in FIG. 4B.

In the Field Effect type molecular device 21, an insulating layer 32 isformed on a first base (substrate) 31 doubling as an electrode forapplying control electric field, and comb-shaped electrodes 33 and 34for measuring conductivity of the biladienone metallic complex 1 areformed thereon. On the other hand, an ITO (Indium Tin Oxide) film 36serving as another electrode for applying control electric field isformed on a second base (substrate) 35, and a homogeneous orientationfilm (insulating film) is laminated thereon. A liquid crystal solution22 of the organic metallic complex 1 consisting of biladienone and zinc(II) ion 3 is put along with spacer (of which illustration is omitted)between two bases 31 and 35, and the peripheral portion is sealed by asealing material 38.

The first base 31 doubling as an electrode for applying control electricfield and the ITO film 36 serving as another electrode for applyingcontrol electric field are electrically connected to a power source 41for applying control electric field. In addition, the comb-shapedelectrodes 33 and 34 are electrically connected to a voltage meter 42and a current meter 43 which are adapted for measuring conductivity.

FIG. 5 is a conceptual schematic cross sectional view for explaining, onmolecular level basis, the structure of the Field Effect type moleculardevice 21. Although only five units of complex molecules 1 ofbiladienone 2 and zinc (II) ion 3 are illustrated in FIG. 5, such anillustration is made as representative, and it is therefore a matter ofcourse that a large number of the same molecules as above are includedin practice (It is to be noted that illustration of liquid crystalmolecules is omitted).

As shown in FIG. 5, in the state where electric field is turned OFF,orientation of complex molecules 1 is performed in upper and lowerdirections in the figure along the side surface of the comb-shapedelectrodes, e.g., gold electrodes 33, 34 to form columnar arrangementstructure 44 so that the above-described structural change takes placeby application of electric field from this orientation state.

A manufacturing process for the Field Effect type molecular device 21will be explained below by making reference to FIG. 5.

First, control electric field applying electrodes 31 and 36 for applyingcontrol electric field to biladienone metallic (zinc) complex, andcomb-shaped electrodes 33 and 34 for measuring conductivity ofbiladienone are fabricated.

As the first base (substrate) 31 doubling as an electrode for applyingcontrol electric field, there is used, e.g., silicon substrate doped athigh concentration. Silicon oxide film is formed by thermal oxidation onthe surface of the first base 31 so that insulating layer 32 isprovided. The comb-shaped electrodes 33 and 34 such as gold electrode,etc. are formed on the insulating layer 32 by sputtering or patterning.

On the other hand, as the second base 35, there is used, e.g., glassbase. ITO (Indium Tin Oxide) film is formed on the surface thereof byvacuum deposition, etc. to allow the ITO film thus formed to be anotherelectrode 36 for applying control electric field. Further, an insulatinglayer 37 such as polyvinyl alcohol, etc. is formed on the ITO film 36 bycoating, etc. Such insulating layer 37 may be liquid crystal orientationfilm by rubbing, etc.

Then, material of the functional molecular element is assembled into theportion between the above-described electrodes 31 and 36 to prepare(manufacture) the main part of the Field Effect type molecular device 21which can perform measurement of modulation of conductivity.

First, zinc complex 1 of the biladienone 2 is dissolved into 4-pentyl4′-cyanobiphenyl (5CB) liquid crystal 40 having positive dielectricconstant anisotropy to coat the liquid crystal solution 22 onto theinsulating layer 32.

The first and second bases 31 and 35 are stuck so that the insulatingfilm 37 formed on the second base 35 becomes closely into contact withthe 4-pentyl-4′-cyanobiphenyl (5CB) liquid crystal solution 22 of thebiladienone.

Finally, the peripheral portion of the two bases 31 and 35 which havebeen stuck is sealed by a sealing material 38 such as epoxy resin, etc.to complete the Field Effect type molecular device 21.

A voltage applied across the electrodes 31 and 36 for applying controlelectric field of the Field Effect type molecular device 21 thusfabricated is caused to be turned ON and OFF to perform conductivitymeasurement (corresponding to measurement of the transistorcharacteristic) of the biladienone metallic complex 2 between thecomb-shaped electrodes 33 and 34. FIG. 6A shows, in a model form, thebehavior (structural change) of molecules when electric field is in OFFstate, and FIG. 6B shows, in a model form, the behavior (structuralchange) of molecules when electric field is in ON state.

As a result, as shown in FIG. 7 which will be described later, forexample, there is observed a modulating action such that low resistancevalue is indicated when electric field is in OFF state, but theresistance value is increased by one figure (digit) or more even whenvery low voltage is applied and the resistance value is increased whenvoltage is further increased. Namely, as the stable state of thestructure, there exist at least three kinds of stable states, i.e.,three stages having gate voltages of 0V, 40 μV/μm and 2 mV/μm thus tohave ability to apply such multi-value memory characteristic.Particularly, it is extremely advantageous that the multi-value memorycan be realized even at low voltage.

As stated above, the electric field strength for driving biladienonemetallic complex is very small, and is a value lower by about twofigures (digits) as compared to, e.g., electric field strength when4-pentyl 4′-cyanobiphenyl liquid crystal performs switching operation.Accordingly, it is a matter of course that the above-mentionedresistance modulating action is not based on switching of4-pentyl-4′-cyanobiphenyl liquid crystal molecule.

Moreover, when a voltage applied across the electrodes 31 and 36 forapplying control electric field is caused to be placed in OFF state tochange measurement voltage across the comb-shaped electrodes 33 and 34to perform conductivity measurement (corresponding to measurement of thediode characteristic) of the biladienone metallic complex between thecomb-shaped electrodes 33 and 34, a predetermined resistance value isindicated irrespective of measurement bias voltage value. Namely, anydiode characteristic is not indicated.

As described above, there is nothing but to mean that the fact that thetransistor characteristic in which conductivity is changed byapplication of control electric field (gate voltage) is indicated asdescribed above, but the fact that diode characteristic is not indicatedindicates that the biladienone metallic complex has very excellentorientation state and has high order parameter.

Since biladienone molecular group used has liquid crystalcharacteristic, but it is not necessary for switching itself to exhibitliquid crystal property (there is no possibility that liquid crystalproperty may not be exhibited by single molecule), it is a matter ofcourse that the biladienone metallic complex can be utilized also as anelement based on molecular level.

It is to be noted that molecular element according to this embodimentcan be applied to various electronic device fields such as switch,transistor, memory, logic circuit and/or display, etc.

In accordance with the above-described present invention, it is possibleto provide a novel functional molecular element adapted to perform, byapplication of electric field, structural change, with respect toelectric field direction, disc shape like organic metallic complexmolecule 1 which forms the columnar arrangement structure to modulatethe structure of the complex molecule to resultantly control anisotropyof dielectric constant.

In other words, there is provided a system of realizing molecularelement from an entirely new viewpoint differently from a system inwhich molecular itself is considered as n-type or p-type semiconductorin a manner resembling semiconductor of the silicon system asconventionally proposed to change electronic state of the molecule tothereby change conductivity.

From the above facts, the functional molecular element based on thepresent invention has, in addition to the merits in which elementshaving size ranging from normal size up to nano-size can be constitutedby the same material molecule, and/or material molecule suitable forobject can be selected from a very large kinds of material molecules,merits in connection with the following points.

1 Low Power Consumption

Since the operation is performed with one molecule or one electron beingas unit, the functional molecular element is operated fundamentally atlow power consumption. In the biladienone used above, there is verysmall power consumption of the order exceeding by one figure (digit) ascompared to energy of room temperature. Since calorific quantity issmall, the problem by heat is difficult to take place even if highintegration is performed.

2 There is No Necessity to Select Drive Frequency

As seen from the improvement in high speed response characteristic ofrecent liquid crystal, material or structure is devised so that highspeed response more than conventional inorganic semiconductor can beexpected.

3 Low Environmental Pollution Characteristic

In synthesis of ordinary organic compounds, reagent, etc. harmful tohuman being or environment as used in the manufacturing process forinorganic semiconductor is hardly required.

Then, practical example of the present invention will be explained inmore detail.

Practical Example 1

The Field Effect type molecular device 21 shown in FIG. 5 was prepared.First, there were formed control electric field applying electrodes 31and 36 for applying control electric field to biladienone metalliccomplex 1 having M=Zn, R═—C10H21 shown in FIG. 2, and conductivitymeasurement electrodes 33 and 34 for measuring conductivity.

As the first base (substrate) (electrode for applying control electricfield) 31, there was used silicon substrate doped at high concentration.Heat treatment was implemented onto the surface of the first base 31 toform silicon oxide thin film to allow the silicon oxide film thus formedto be insulating layer 32. The comb-shaped electrodes 33 and 34consisting of gold were formed on the insulating layer 32 by sputteringor patterning as electrodes for measuring conductivity of thebiladienone metallic complex 1.

Then, ITO transparent electrode 36 was formed on the second base (glassbase) 35 by vacuum deposition as another electrode for applying controlelectric field thereafter to form insulating layer 37 on the ITOtransparent electrode 36. As this material, polyvinyl alcohol wasselected. 10 weight % aqueous solution of polyvinyl alcohol was preparedto coat the aqueous solution thus prepared onto the ITO 36 by thespin-coat process to perform heat treatment for 30 minutes at 110° C.thereafter to dry it for 72 hours in vacuum.

Further, the first and second bases 31 and 35 are stuck with each otherthrough spacer so that gap between the both bases becomes equal to 5 μm.

Then, liquid crystal solution 22 consisting of zinc complex 110 weight %of biladienone 2 and 90 weight % of 4-pentyl-4′-cyanobiphenyl (5CB) 40is injected into the portion between the first and second bases 31 and35 by making use of the capillary phenomenon.

Finally, the peripheral portion of the two bases 31 and 35 which havebeen stuck was sealed by a sealing material 38 to complete the FieldEffect type molecular device 21.

When a voltage applied across the control electric field applyingelectrodes 31 and 36 of the Field Effect type molecular device 21fabricated in this way is caused to be turned ON and OFF to measure, bya.c. bias voltage, conductivity of the biladienone 2 between thecomb-shaped electrodes 33 and 34, a large current quantity was indicatedwhen electric field is in OFF state, but modulating action was observedsuch that current quantity is lowered at two stages by application ofelectric field.

FIG. 7 is a graph showing, with respect to the magnitude of appliedvoltage, the result obtained by applying d.c. electric field across thecontrol electric field applying electrodes 31 and 36 of the Field Effecttype molecular device 21 fabricated in this way to measure current valuebetween the comb-shaped electrodes 33 and 34 in this instance.

In accordance with the graph, when viewed from applied voltage, theentirety is classified into three areas. In FIG. 7, illustration is madesuch that the structural diagrams of biladienone 2 between theelectrodes 31 and 36 are added to respective areas in a model form.Namely, at the time of the area I where applied voltage is in OFF state,relatively high current value, i.e., low resistance characteristic wasindicated. Within the area II where applied voltage is 40 μV/μm, thefirst structure change took place to indicate intermediate resistancevalue. Further, at the time of the area III where applied voltage is 2mV/μm, the second structure change took place to indicate relatively lowcurrent value, i.e., high resistance characteristic. In this case,ON/OFF ratio>100 is obtained. This is very satisfactory.

Accordingly, there exist at least three kinds of stable states of thestructure. Thus, such multi-value memory characteristic can be applied.

Moreover, measurement of dielectric constant between the comb-shapedelectrodes 33 and 34 was performed simultaneously with the currentquantity measurement. The result of FIG. 8 verifies the mechanism inwhich dielectric constant is changed followed by current quantity changeand resistance change shown in FIG. 7 is induced by dielectric constantchange.

As described above, since there is constituted functional molecularelement adapted to change, by application of electric field,conformation of disc shape like organic metallic complex molecule 1which forms the columnar arrangement structure to exhibit function, thestructure of the organic metallic complex molecule 1 is changed whenelectric field is applied. Namely, anisotropy of the dielectric constantis changed. Accordingly, conductivity between measurement electrodes ispermitted to be switched. As the stable value thereof, there are two orthree kinds of stable states, and/or kinds more than three kinds. Thus,its multi-value memory characteristic can be applied.

Such electric field action mechanism was not found in conventionalfunctional molecular elements or devices for directly controllingelectronic state of the functional molecular element by electric field,e.g., Field Effect Transistor, etc. On the basis of such a new electricfield action mechanism, it is possible to constitute a functionalmolecular element capable of controlling electric characteristic withgood electric field response.

Comparative Example 1

A bias voltage applied across the comb-shaped electrodes 33 and 34 wasincreased or decreased without applying electric field across thecontrol electric field applying electrodes 31 and 36 in order to observethe diode characteristic in the practical example 1 to measure currentquantity.

As shown in FIG. 9, any change based on application of bias electricfield was not found (observed). This result indicates that biladienonemolecule 2 has very high orientation. This is because since thebiladienone molecule (functional molecular element) indicates thetransistor characteristic as shown in FIG. 7, it responds, with highsensitivity, to electric field applied across the control electric fieldapplying electrodes 31 and 36, i.e., even very low voltage of 40 μV, butdoes not respond to electric field across the comb-shaped electrodes 33and 34 by any means. In addition, this result verifies the principle asshown in FIG. 1 in which structure change takes place with respect todirection of applied electric field.

It is a matter of course that the above-described embodiments 1, 2 ofthe invention do not limit the present invention by any means, but maybe changed or modified as occasion demands within the scope which doesnot depart from the gist of the present invention.

It is to be noted that while the present invention has been described inaccordance with certain preferred embodiments thereof illustrated in theaccompanying drawings and described in detail, it should be understoodby those ordinarily skilled in the art that the invention is not limitedto embodiments, but various modifications, alternative construction orequivalents can be implemented without departing from the scope andspirit of the present invention as set forth by appended claims.

INDUSTRIAL APPLICABILITY

The functional molecular element according to the present invention isused in elements or devices such as Field Effect type molecular device,etc.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its intended advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

1. A functional molecular element comprising a system in which ananisotropy of a dielectric constant is changed by a molecular structurechange induced by an electric field, wherein the functional molecularelement includes a complex of an organic molecule having anisotropy ofdielectric constant or dipole moment and including side chains each ofwhich structure is changed under application of electric field, andmetallic ion.
 2. The functional molecular element according to claim 1,wherein the side chain has a linear chain shape, and is substantiallybonded to the disc-shaped organic molecule.
 3. The functional molecularelement according to claim 2, wherein a liquid crystal solution oforganic metallic complex molecule that includes the organic moleculehaving the side chains is disposed between at least opposite electrodesin a state where orientation of the organic metallic complex molecule isperformed on an electrode for applying electric field, and an outputcorresponding to the electric field is taken out from at least oneelectrode of the opposite electrodes.
 4. The functional molecularelement according to claim 3, wherein a columnar arrangement structurein which the organic metallic complex molecules are arranged in a columnform is formed between the pair of opposite electrodes.
 5. Thefunctional molecular element according to claim 3, wherein the structureof the organic metallic complex molecule is changed by a change of theelectric field exerted on the organic metallic complex molecule so thatan angle that a major axis direction of a dielectric constant tensor anda formation plane surface of a pair of opposite electrodes form ischanged.
 6. The functional molecular element according to claim 4,wherein an insulating layer is provided on a first electrode forapplying the electric field, a second electrode and a third electrodeare formed, as the opposite electrodes, on the insulating layer so asnot in contact with each other, the columnar arrangement structure isdisposed between at least the second and third electrodes, and a fourthelectrode for applying the electric field is provided on the columnararrangement structure directly or through an insulating layer.